Setting Examples; Line Differential Protection L3Cpdif, L6Cpdif, Lt3Cpdif, Lt6Cpdif - Hitachi 670 Series Application Manual
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Section 4
Analog and binary signal transfer for line differential protection
IEC15000460 V1 EN-US
Figure 33:
Figure
34
four current inputs to IEDs are used. Current from each CT is fed to an IED, and currents from
different CTs are processed separately by the protection algorithm. Summing up the CTs' secondary
currents at the end with two CB and CT groups is not allowed. CBs at all ends can be included in the
protected zone depending on their positions relative to the CTs.
IEC15000461 V1 EN-US
Figure 34:
The locally measured current samples are exchanged between all IEDs at line ends (in master-
master mode) or sent for evaluation to one master IED from all slave IEDs (in master-slave mode).
In master-master mode, all IEDs at different ends of a protected zone execute exactly the same
program code with exactly the same information so the same response is expected from all masters.
In master-slave mode, only one IED has access to all currents in the protected zone. It is always
recommended to select the master-master mode if allowed by the number of communication links.
When communication failure occurs, L4CPDIF function will be blocked. Under the blocking period,
COMFBLKD will be set to indicate that L4CPDIF function is blocked by communication failure.
4.7
Setting examples
4.7.1
Line differential protection L3CPDIF, L6CPDIF, LT3CPDIF,
LT6CPDIF
Setting example with a power transformer in the protected zone
Figure
35
presented in Figure 36. The protected zone is limited by three current transformers: CT1, CT2 and
CT3. IEDs are situated in two separate substations 1 and 2.
32
Two-end power line with two CB and CT groups at each end
shows a three-end power line configuration where one end has two CB and CT groups. All
Three-end power line with two CB and CT groups at one end
shows a line with a power transformer in the protected zone. Circuit impedances are
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IEC15000460-1-en.vsd
IEC15000461-1-en.vsd
Communication set-up, 670/650 series
1MRK505382-UEN Rev. K
M12941-3 v8
Application Guide
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